I just tried installing Red Hat 8.0 on my new computer, which has an Asus 9280TD GeForce 4 Ti 4200 video card. When setting up the video settings, my video card is not detected as a GeForce, it just uses the generic driver ("vesa"), which limits me to 800x600 resolution. If I try to change the driver to "nv", X will not start -- it tries a few times then says it could not start and asks if I want to reconfigure it.

So, I downloaded the drivers from nVidia and installed them. They say to change your driver to "nvidia". But then when X starts, the screen is total garbage, and I cannot change to another terminal (CNTL-ALT-Fx) or reboot, I have to power down. When I run the nv_check.sh script, it tells me that the nVidia kernel module is not loaded, even if I run it right after running "modprobe nvidia".

I have tried both installing the binary RPM and compiling the source RPM. Please help!

First, I have/had the same problem..
Second, Even that I think that ur problem is EXACTLY the same, (==no idea what to do..), I'll tell you a couple of things that "might just" help..

First, we'll see if your drivers are installed properly; Add the following in your XF86Config file, into
section "Device": Option "NvAgp" "0"
This will disable the use of agp support from the device. If X starts OK, then read on...

Make sure that IF you use nvidia's own agp support, THEN you don't have the
Linux standard agpgart loaded in kernel. If it does, it will not work, and visa versa.

Selecting between different agp suports happens in XF86Config, by changeing
the values of "NvAgp" "X", where X is 1, 2, 3, or 0..

1=nVidia's agp
2=agpgart
3=try agpgart, Then try nVidia
0=Disabled

You should read the README at /usr/share/doc/NVIDIA_GLX_xx-xx, Appendix D and F for more info.
Well, Good Luck with your Driver. Mine "works" without Agp support for the moment..